Iodine recovery



March 4, 1941- v. c. E. LE GL'OAHEC ETAL 2,233,787v

IODINE RECOVERY Filed Jan. 20, 1938 wao-MNM ATTORNEYS.

Patented Mar. 4, 1941 l UNITED STATES PATENT OFFICE IODUWE RECOVERY Victor Charles Emile Le Gloahec, Rockland, Maine, and John Robert Herter, New York, N. Y., assignors. to Algin Corporation of America, New York, N. Y., a corporation of Delaware Application January 20, 1938, Serial No. 185,810 In France January 11, 1934 5 Claims. (C1. 23-97) This invention relates to iodine recovery, i. e., with soft water so as to complete Ithe removal of the recovery of iodine and/or iodine compounds the iodine containing material therefrom. from solutions containing iodine salts. The following is an example of the separation In the practice of this invention an aqueous sof OCIle-eontainng material, tog-ether With lution of a soluble iodine salt i-s treated With a lan'lnarine and certain other matters from sea- 5 Water soluble :copper salt to precipitate cuprous Weed, Which may be either freshly teken from iodide, .the precipitation being inthe presence of the Water or be in dried condition. In order to an acid and of metallic copper as an ant-oxidiz make a gOed Separation, We take. fol" eXemple. ing agent. The solution of soluble iodine sal-t 1000 parts by Weight 0f Idried `SeaWeeOl still 00nmay contain soluble iodine salts such as Ithe taining about 30% yO moisture and make use 0f 10 iodine salts of alkali metals, alkaline earths, amfrom 2.2 to 2.8 perils by Weight 0f `Caleiulh 0h10- 'monium or magnesium. After the cuprous iodide Tide (ehhydlOuS) 0I' from 4.9 to 6.2 parte 0f barhas been precipitated -it can then be treated for um 'Chloride (crystallized With two molecules of the recovery of iodine er iodine compounds ,as Water). About 3000 parts by volume `of solution described be1ow. Features of `this invention reiS used for eXhauStng the amount `of seaweed 15 .late tothe precipitation step and to the recovery abovementioned. This solution therefore consteps and me .che employment 1of `these Steps in tains from 0.8 to 1% of lanhydrous calcium chloeombinaom ride, for example. If the process is carried out 2O An available source of iodine is certain sea- Wth seaweed 'as freshly taken from Wamel The Weeds, Such as Laminaaemd pheophyeeae, meeproportions of alkaline-earth salt must be rerocystis, and nereocystis. Such seaWeeds conduced about Ve @mesh The mfeatment may be ,tain ,a ,great number ,of bodies, lto Wilt: sans, incarried out either 1n the hot state or in the cold cluding iodine salts, most of which are salts of Stafte HOWeVel" We have found that it 1S advanalkaline metals (e. g. sodium or potassium) :and tageous 350 Operate m fthe @01d State- `of yMnmcmium and magnesium ,and Various M The seaweed is .then Washed with soft Water 25 garlic matters, ehe most ,important of which are; which removes the excess alkaline-earth salts and algin, laminarine, mannitol and algulose (seaat @he @me time femm/'es the remainder 0f the Weed .ceumose) lfaminatne and tibet iodilrlie-containing material The recovery of alginous material from searom e Seawee Oge' er W115i? cercai@ other Weed is ydescribed in our ,Copendng ,application matters such as mannitol. This operano-n of serian No. 1076, nica January 9, 1935, (now Pat- Washing Wlth Soft Waiter 1S Stopped 'merely for ent No. 2,128,551 dated August 3o, 1938 the :The Sikeof ecnomy Whe? the @Xhausimg Wates present application being a continuation-in-part 'gls'tam only /2% appr'oxmately of Soluble ma of said application. w To illustrate the practice of this invention ,Ofntlhgrgue fg' leqfllf ,ogy "a there will be described the preparation `of a solu- 4` tion of iodine containing salts from seaweeds glmhfetleag lssovlsa'blfe mlokrry and .the recovery of iodine or iodine compounds f 01119 a a meth f Th earth salts and the subsequent Was-ning with soft 40 Xre It'm' v f emhseawed 1S rtfufea'ted for @he water in a systematic manner according to 40 e l .l l I Water as rich as possible. The Wash waters are contammg maten'ail s m @he form of Wa'ter S0111' then treated as hereinbelow described for the reble salts and can be read1ly extracted from the l seaweeds Wirth t P b1 th a .moval of certain materials mcludlng Iodine or l erre era" y .3 lofmef iodine compoundstherefrom. If the wash Waters 4D containing material, together with lammarlne 1s are remsed it is then necessary ,to add a desired Separt@ from 'the mgullose and @gm 1D fthe Se?? amount of :alkaline earth salts thereto before :they geen?ylilgletefggt fotl in against come into `Contact with sean-@eds that I' w. y e,a anhave not been exhausted.

v'50 tage 1s taken of the fact that laminarine remains The algulcse and algin residue which has been 50 soluble in Water in the presence of alkaline-earth washed may be treated fer me recovery cf aigin salts and can be separated from the algulose and in c, pure form in accordance with Pitem; Nc

algm along with iodine-:containing material. 2,128,551. I

After extraction of the seaweed with yalkaline- According to the present invention, the Wash 55 earth salts, the seaweed is subsequently Washed Waters which include iodine-containing material '55 volume of said residue, with a centrifugal treatmenrt between these two washing operations, 'and .the washing waters are mixedwith lthe initial mother liquors. The Whole contains a rather low percentage of iodine, to wit, from one .to rtwo kilograms per cubic meter. While the purification step above described is preferable prior to the precipitation step described below, -in order to obtain the precipitate in better form, the purification step is not essential.

In order to precipitate the iodine from a solution of soluble iodine salt, e. g., the solution of soluble iodine salt recovered from seaweed as above-described, in the form of copper iodide by means of a soluble copper salt such as copper sulphate with a good yield, precipitation should take place not only in the presence of an acid such as sulphuric or hydrochloric acids but also in the presence of metallic copper as an antioxidizing agent.

By way of example, We obtain satisfactory results through the following method:

The liquid to be treated is contained in a suitable tank of wood or of stoneware, and there is added thereto for each part in weight of iodine:

(a) A solution of copper sulphate containing 3.5 parts of crystallized salt, the amount of copper sulphate being that which results from the use of the commercial product which is in either crystalline or powdered form and which corresponds to the formula CuSO4-5l-I2O;

(b) A sufficient amount of sulphuric acid in order that the solution may contain about two per cent. of sulphuric acid in excess. Hydrochloric acid may also be utilized.

(c) Metallic copper, preferably produced by precipitation of copper from a solution of a soluble copper salt, as an anti-oxidizing body and catalyst. Metallic copper in the form of shavings or plates may also be used.

The precipitation is sufficient after a period of twenty-four hours. The precipitate of cuprous iodide is then subjected to centrifuging.

Metallic copper produced by precipitation of copper from a solution of a soluble copper salt, is, as aforesaid, preferable to other forms of metallic copper, because we have found that when copper precipitated from solution is used in the aforesaid precipitation reaction the reaction is much more rapid and gives a higher yield of cuprous iodide than when other forms of metallic copper are used.

Other soluble copper salts such as copper chloride or copper acetate may also be used, although copper sulphate is usually to be preferred. If desired, a reducing agent compatible with acid such as sodium bisulphite, hydrogen gas, SO2 gas or the like may be present during the precipi tation step.

In the mother liquor, copper is recovered by precipitating copper in said liquor with iron, preferably after having been neutralized by means of lime, soda ash or the like. The precipitated copper produced in this Way may be used as the anti-oxidizing agent in the precipitation step. Alternatively the precipitated copper may be transformed into copper sulphate and copf per sulphate produced in this way may be used to effect precipitation of copper iodide in the precipitation step.

The residual liquor freed `from copper is then freed from the iron that is contained therein, bymeans of lime; then it is filtered. Finally, if desired, the liquid can be evaporated in order to separate the salts and the mannitol present therein by fractional crystallization.

As for the precipitate of cuprous iodide, it is calcined in the presence of caustic soda or potash, With an excess of alkali of about two or three per cent. Then sodium nitrate is added, in the proportion of about 130 parts in weight for 150 parts of cuprous iodide, in the form of a paste produced as by centrifuging. While sodium nitrate is regarded as preferable, other oxidizing agents such as sodium perborate, calcium oxide, lead dioxide, or the like may be used. The Vamount of oxidizing agent used preferably should not exceed that which is neces. sary to transform the cuprous oxide to copper oxide. The mixture is calcined at a temperature of about S50-375 C., for about ten minutes.

After cooling, the calcined product is'treatedwith water, and the resulting product is filtered. The liquor which is a solution of sodium iodide may be treated as by evaporation to recover sodium iodide. Alternatively the liquor may be treated by known` methods for the precipitation of iodine; for instance, it can be treated with chlorine for this purpose. VThe 'iodine thus obtained may `be nally refined by sublimation. The residue of the lixiviation is copper oxide, which may be transformed into copper sulphate by known methods. v

It is also possible to treat the precipitate of cuprous iodide to obtain soluble iodides in kother ways. Y f

For example, this precipitate is washed twice with five times its volumeof water,land it is then treatedf with a slight excess of biaryta water containing about twenty-live per cent. of barium hydroxide at a temperature of 90l00 C. The following reaction takes place:

The liquor is filtered inorder to separate the copper oxide, which may be transformed-into copper sulphate. The clear solution yis treated with a molecular amount ofthe sulphate ofthe metal, the iodide of which is to be preparedfor instance, according to the followingl reactions;

The use of baryta water in carrying out the foregoing steps is preferable to the'use of other metallic hydroxides due to the fact that barium sulphate is more insoluble than the other metallic sulphates and results in a more pure'product. Y

tive purposes merely and that the scope of this invention is not limited thereby.

If desired, the wash waters obtained by washing seaweed with a solution of alkaline earth salt solution, which wash waters contain laminarine as well as soluble iodine containing substances, may be treated to eliminate the laminarine before the iodine is precipitated as cuprous iodide. This may be done as described in our application executed January 18, 1938, for Removal and recovery of laminarine from seaweed, now patent No. 2,188,092 issued January 23, 1940 on application Serial No. 185,838 led January 20, 1938, e. g., by precipitating the laminarine by means of alcohol or by means of subacetate of lead in an alkaline medium. This may be done before or after the step above-described wherein the alkaline earth metal salts in the solution are precipitated in the form of alkaline earth metal carbonate, if said step is employed.

In order to facilitate an understanding of the present invention and pursuant to the foregoing, the practice thereof is exemplified by the ow sheet shown in the accompanying drawing. It is to be understood, however, that the process indicated in the accompanying drawing is merely illustrative and that the scope of this invention is to be governed by the language of the following claims.

We claim:

1. A method of treating seaweed which comprises washing the seaweed with an aqueous washing liquid to dissolve iodine-containing substances and laminarine, separating the washingsolution containing dissolved materials from the undissolved material, adding to the solution a precip-itant for the laminarine, separating the precipitated laminarine from liquid containing dissolved iodine-containing substances, and precipitating the iodine as cuprous iodide by incorporating in the solution a water-soluble copper salt, the precipitation being in the presence of a mineral acid and of metallic copper precipitated from a solution of a soluble copper salt.

2. In a method of recovering a substance comprising iodine, the `step comprising precipitating cuprous iodide from an aqueous solution of a water-soluble iodine salt by incorporating in the solution a water-soluble copper salt, the precipitation being in the presence of a mineral acid and of metallic copper in the original nely divided form as precipitated from a solution of a soluble copper salt by a metal.

3. The step according to claim 2, wherein the acid is an acid selected from the group consisting of hydrochloric acid and sulphuric acid.

4. A method according to claim 2 and wherein the precipitated cuprous iodide is calcined with caustic alkali and an oxidizing agent, and the calcined product is extracted with water.

5. A method according to claim 2 and wherein the cuprous iodide is treated with b-aryta water to form barium iodide and the barium iodide is treated with a sulphate of a metal of the iodide of which is to be recovered to form a soluble iodine salt of said metal and precipitated barium sulphate, and the soluble iodine salt is separated from the barium sulphate.

VCTOR CHARLES EMILE LE GLOAHEC. JOHN ROBERT HERTER, 

